Spread Nutella evenly on all four slices of brioche. Divide the cut banana slices evenly and apply to two slices of the brioche. Top these two slices of bread with the remaining two slices of brioche in order to form two sandwiches.

Beat the eggs in mixing bowl with heavy cream and vanilla extract. Dip each sandwich in the egg batter and coat well on all sides.

Heat butter in a nonstick frying pan over medium-high heat until thoroughly melted and hot. Add the two egg-soaked sandwiches and cook in pan until egg is cooked on both sides.

For presentation, cut the French toast in half diagonally. Peel the remaining banana and cut in half lengthwise. Sprinkle with granulated sugar on cut side and caramelize with torch. Place on plate and dust with powdered sugar. Serve immediately.